Ion implantation systems are used to impart impurities, known as dopant elements, into semiconductor substrates or wafers, commonly referred to as workpieces. In such systems, an ion source ionizes a desired dopant element, and the ionized impurity is extracted from the ion source as a beam of ions. The ion beam is directed (e.g., swept) across respective workpieces to implant ionized dopants within the workpieces. The dopant ions alter the composition of the workpieces causing them to possess desired electrical characteristics, such a may be useful for fashioning particular semiconductor devices, such as transistors, upon the substrates.
The continuing trend toward smaller electronic devices has presented an incentive to “pack” a greater number of smaller, more powerful and more energy efficient semiconductor devices onto individual wafers. This necessitates careful control over semiconductor fabrication processes, including ion implantation and more particularly the uniformity of ions implanted into the wafers. Moreover, semiconductor devices are being fabricated upon larger workpieces to increase product yield. For example, wafers having a diameter of 300 mm or more are being utilized so that more devices can be produced on a single wafer. Such wafers are expensive and, thus, make it very desirable to mitigate waste, such as having to scrap an entire wafer due to non-uniform ion implantation. Larger wafers and high density features make uniform ion implantation challenging, however, since ion beams have to be scanned across larger angles and distances to reach the perimeters of the wafers, yet not miss implanting any region therebetween.
In addition, the high voltage necessary to supply the ion source of such an ion beam is subject to occasional arcing between the various extraction and suppression electrodes and other nearby parts. This tendency for arcing often fully discharges one or more affected HV supplies until the arc naturally self-extinguishes at a much lower supply voltage. While arcing, the beam current may become serious erratic or may be interrupted until the supply voltage is restored, during which time ion implantation may experience intermittent or non-uniform ion implantation dose levels. Accordingly, there is a need for mitigating the effects of HV arcing associated with an ion source or the electrodes of an ion implanter to provide uniform implantation over such larger implantation angles and distances of the ion beam.